Industrial robot shaft supporting mechanism

ABSTRACT

A shaft supporting mechanism of an industrial robot in which an arm is supported by a freely extendable support shaft inside a hollow post and a working plane of a working arm is variably set is provided, with plural sets of linear support guides in opposed relation about a drive mechanism of the support shaft. As a result, the support shaft is held in the post stably and balanced in the vertical direction even if an external force attempting to tilt the support shaft is applied during up-and-down movement of the support shaft or operation of the working arm.

DESCRIPTION Background of the Invention

This invention relates to an industrial robot mechanism for supporting,internally of a post, a shaft supporting an arm in a freely extendablemanner.

A variety of industrial robots have recently come into wide use invarious fields. FIG. 3 is a side view illustrating one example of ahorizontal articulated industrial robot installed on a floor andprovided with a swiveling post.

In FIG. 3, numeral 1 denotes a post supported on a base 2 and capable ofbeing swiveled within a predetermined rotational range (θ). Providedwithin the base 2 is a swiveling mechanism 21 for swiveling the post 1.Numeral 3 denotes a first arm (working arm) supported at the upperportion of the post 1 by a support shaft 4. A second arm 5 capable ofbeing swiveled in the horizontal direction is attached to the distal endof the first arm 3, and the distal end of the second arm 5 is providedwith a wrist 51.

Provided in the post 1 is a drive mechanism 11 (FIG. 4) for moving thesupport shaft 4 up and down within a predetermined range (Z) to controlthe height of the first arm 3. Though the details are not shown, thedrive mechanism 11 drives the support shaft 4 up and down by e.g. arack-and-pinion combination or a screw rod-nut combination, therebycontrolling the height of the first 3 (working arm). A guide for linearsupport is provided between the support shaft 4 and the inner wall ofthe post 1 so that the support shaft 4 will move linearly with respectto the post 1 when it is driven up and down by the drive mechanism 11.

FIG. 4 is a sectional view taken along line 4--4 of FIG. 3 andillustrating an example of the drive mechanism 11. The support shaft 4,which is driven by the drive mechanism 11, consisting of a combinationof a screw rod 6 and nut 41, possesses a sliding contact portion 42 atwhich the support shaft 4 slides on the side faces of a linear supportguide 14 provided on a supporting plate 13, thereby forming a guidemechanism. The arrangement is such that the support shaft 4 moves in thevertical direction.

In the above-described shaft supporting mechanism of support shaft 4,the shaft 4 moves linearly while the sliding contact portion 42 thereofis in contact with three faces of the linear support guide 14, and theworking plane of the first arm 3 moves up and down in parallel with thelongitudinal direction of the post 1. However, the guide 14 and slidingcontact portion 42 tend to separate from each other in response to aforce acting in the direction of the arrow X shown in FIG. 4. Forexample, if the reaction force of a load acting upon the second arm 5 isin the direction of the arrow X, the support shaft 4 will no longer besupported stably.

SUMMARY OF THE INVENTION

The present invention has been devised in view of the foregoing problemsof the prior art and its object is to provide an industrial robot shaftsupporting mechanism capable of supporting the shaft of a working armand of moving the shaft linearly in the vertical direction whilemaintaining a stable balance.

In accordance with the present invention, there is provided anindustrial robot shaft supporting mechanism for supporting an arm in afreely extendable manner inside a hollow post and for variably setting aworking plane of the arm. The mechanism includes: a drive mechanism fordriving the support shaft to extend and retract the same; a plurality ofguide seats arranged at positions symmetrical which respect to the drivemechanism and each having an opening, and linear support guides engagingthe guide seats and attached to opposing inner wall portions of thepost.

In accordance with the industrial robot shaft supporting mechanism ofthe invention, a plurality of linear support guide mechanisms areprovided to oppose one another with the drive mechanism at the center.As a result, the support shaft is held in the post stably and balancedin the vertical direction even if an external force attempting to tiltthe support shaft is applied during up-and-down movement of the supportshaft or operation of the working arm. Furthermore, the linear supportguides also function as post reinforcing members at the inner wallportion of the post.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view illustrating an embodiment of anindustrial robot shaft supporting mechanism according to the presentinvention;

FIG. 2 is a transverse sectional view taken along line 2--2 of FIG. 1

FIG. 3 is a side view illustrating an example of a conventionalhorizontal articulated-type industrial robot; and

FIG. 4 is a sectional view, taken along line 4--4 of FIG. 3,illustrating an example of a conventional shaft supporting mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described withreference to the drawings.

In FIGS. 1 and 2, portions similar to those shown in FIGS. 3 and 4 aredesignated by like reference characters and a description thereof isomitted. Numeral 7 denotes a drive motor for supplying a driving forcethat drives the support shaft 4 up and down by the drive mechanismcomposed of the combination of the screw rod 6 and nut 41. Fitted on ashaft 71 of the drive motor 7 is a motor pulley 72, which is attached toa partitioning wall 15 of post 1 via a bearing 73.

The screw rod 6 is attached to the partitioning wall 15 via a bearing 61and is freely rotatable so as to be rotated by driving a belt 74stretched between a drive pulley 62 provided on the screw shaft 6 andthe motor pulley 72. The lower end portion of the screw rod 6 isprovided with a brake mechanism 63 actuated by electromagnetic action tostop the screw rod 6 from rotating.

The nut 41, which is threadedly engaged with the screw rod 6, isattached to a nut holder 43 provided on the support shaft 4, as shown inFIG. 2. Two guide seats 44 are attached to both side faces of the nutholder 43. The guide seats 44, each of which has an opening 44a and aback face 44b, are attached to the nut holder with their openings 44afacing outward and their back faces 44b facing each other about thescrew rod 6 as center.

Guide rails 16, serving as linear support guides, each have a groove 16ain two opposite side faces thereof, each guide rail therefore having across section similar to that of a railroad rail. The arrangement issuch that the opening 44a of each guide seat 44 is engaged with thegrooves of the corresponding guide rail 16, so that the guide seat 44may be moved linearly along the guide rail 16. Each guide seat 44engages with the corresponding guide rail 16 and slides smoothly on theside surface of the guide rail 44. The guide rails 16 are attached inopposing relation to the inner wall of the hollow, cylindrically shapedpost 1, and the support shaft 4, which has the nut holder 43 whose twosides are provided with the guide seats 44 engaged with the guide rails16, is arranged within the post 1.

Accordingly, the support shaft 4 moves linearly up and down, while beingguided by the guide seats 44 having the respective openings 44a engagedwith the guide rails 16, along these guide rails 16 attached in opposingrelation to the inner wall of the post 1 in such a manner that therigidity of the post 1 is increased. In the present embodiment, the post1 can be separated into two halves longitudinally by removing lockingbolts 17, thus making it possible to install components within the post1 and to adjust them.

The operation of the present embodiment constructed as set forth abovewill now be described. When current is passed through the drive motor 7to rotate the same, the motor pulley 72 rotates, thereby rotating thedrive pulley 62 via the belt 74 to turn the screw rod 6.

Owing to rotation of the screw rod 6, the support shaft 4 provided withthe nut 41 threadedly engaged with the screw rod 6 is acted upon by aforce that moves the support shaft up or down, and the guide seats 44travel linearly longitudinally of the post 1 under the guidance of theguide rails 16. Since the guide seats 44 and guide rails 16 flanking thescrew rod 6 are provided at positions symmetrical with respect to thenut holder 43, the up-and-down movement of the support shaft 4 isbalanced and stable.

Since the guide rails 16 are provided in opposed relation on the innerwall of the post 1 having the hollow, cylindrical structure in thepresent embodiment, the post 1 is provided with additional rigidity.

In the shaft support mechanism of the present invention as described indetail hereinabove, plural sets of linear support guide rails 16 andguide seats 44 are provided in opposing relation about a drive mechanismfor up-and-down movement and serve as a mechanism for supporting a shaft4, which moves the working arm 3 of an industrial robot vertically upand down. As a result, vertical support of the support shaft is achievedstably with excellent balance even if an external force attempting totilt the support shaft 4 is applied during up-and-down movement of thesupport shaft 4 or operation of the working arm 3.

Further, the guide mechanism has left-right symmetry with respect to thescrew rod 6 for drive. This has the advantage of simplifying thearrangement inside the post 1. In addition, the provision of the guiderails 16 on the inner wall of the post 1 raises the rigidity of the post1 and makes it possible to obtain a more compact arrangement.

Though the present invention has been described based on theabove-described embodiments, the invention can be modified in variousways without departing from the scope of the claims.

By applying the invention to an industrial robot in which an arm issupported by a freely extendable support shaft inside a hollow post andthe working plane of the arm is variably set, vertical support of thesupport shaft can be achieved stably with excellent balance even if anexternal force attempting to tilt the support shaft is applied duringup-and-down movement of the support shaft or operation of the workingarm.

We claim:
 1. A shaft supporting mechanism of an industrial robot inwhich an arm is supported by a freely extendable support shaft inside ahollow post and a working plane of the arm is variably set,comprising:(a) a drive mechanism positioned outside said support shaftfor driving said support shaft to extend and retract the samevertically; (b) a plurality of guide seats connected to said supportshaft, arranged at positions substantially laterally symmetrical withrespect to said drive mechanism and each having an opening; and (c) acorresponding plurality of linear support guides engaging said guideseats and being attached to opposing inner wall portions of said post.2. A shaft supporting mechanism of an industrial robot according toclaim 1, wherein said linear support guides are adapted in such a mannerthat said guide seats engage grooves in two, opposing side surfacesthereof.
 3. A shaft supporting mechanism of an industrial robot in whichan arm is supported by a freely extendable support shaft inside a hollowpost and a working plane of the arm is variably set, comprising:(a) adrive mechanism for driving said support shaft to extend and retract thesame; (b) a plurality of guide seats connected to said support shaftarranged at positions symmetrical with respect to said drive mechanismand each having an opening; and (c) linear support guides engaging saidguide seats and attached to opposing inner wall portions of said post,wherein said post is so adapted as to be separable into a portion towhich said linear support guides are attached and a portion other thansaid portion.